Ebook Principles and practice of mechanical ventilation (3/E): Part 1

(BQ) Part 1 book “Principles and practice of mechanical ventilation” has contents: Historical background, physical basis of mechanical ventilation, indications, conventional methods of ventilatory support, alternative methods of ventilator support, noninvasive methods of ventilator support,… and other contents.

Principles and Practice

of Mechanical Ventilation

Medicine is an ever-changing science As new research and clinical ence broaden our knowledge, changes in treatment and drug therapy are required Th e authors and the publisher of this work have checked with sources believed to be reliable in their eff orts to provide information that is complete and generally in accord with the standards accepted at the time of publication However, in view of the possibility of human error or changes in medical sciences, neither the authors nor the publisher nor any other party who has been involved in the preparation or publication of this work war-rants that the information contained herein is in every respect accurate or complete, and they disclaim all responsibility for any errors or omissions or for the results obtained from use of the information contained in this work Readers are encouraged to confi rm the information contained herein with other sources For example and in particular, readers are advised to check the product information sheet included in the package of each drug they plan to administer to be certain that the information contained in this work

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Principles and Practice

of Mechanical Ventilation

Editor Martin J Tobin, MD

Professor of Medicine and AnesthesiologyEdward Hines, Jr., Veterans Administration Hospital andLoyola University of Chicago Stritch School of Medicine

Editor emeritus, American Journal of Respiratory and Critical Care Medicine

Chicago, Illinois

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2 Classifi cation of Mechanical Ventilators

and Modes of Ventilation 45

Robert L Chatburn

3 Basic Principles of Ventilator Design 65

Robert L Chatburn and Eduardo Mireles-Cabodevila

4 Indications for Mechanical Ventilation 101

Franco Laghi and Martin J Tobin

OF VENTILATORY SUPPORT 137

5 Setting the Ventilator 139

Steven R Holets and Rolf D Hubmayr

Laurent J Brochard and Francois Lellouche

9 Pressure-Controlled and Inverse-Ratio Ventilation 227

Marcelo B P Amato and John J Marini

10 Positive End-Expiratory Pressure 253

Paolo Navalesi and Salvatore Maurizio Maggiore

V ALTERNATIVE METHODS OF VENTILATOR SUPPORT 303

11 Airway Pressure Release Ventilation 305

Christian Putensen

12 Proportional-Assist Ventilation 315

Magdy Younes

13 Neurally Adjusted Ventilatory Assist 351

Christer Sinderby and Jennifer C Beck

14 Permissive Hypercapnia 377

John G Laff ey and Brian P Kavanagh

15 Feedback Enhancements on Conventional Ventilator Breaths 403

Neil MacIntyre and Richard D Branson

OF VENTILATOR SUPPORT 415

16 Negative-Pressure Ventilation 417

Antonio Corrado and Massimo Gorini

17 Noninvasive Respiratory Aids: Rocking Bed, Pneumobelt, and Glossopharyngeal Breathing 435

Nicholas S Hill

18 Noninvasive Positive-Pressure Ventilation 447

Nicholas S Hill

CONTENTS

32 Mechanical Ventilation

in Neuromuscular Disease 761

Ahmet Baydur

33 Chronic Ventilator Facilities 777

Stefano Nava and Michele Vitacca

34 Noninvasive Ventilation on a General Ward 793

Mark W Elliott

IX PHYSIOLOGIC EFFECT OF MECHANICAL VENTILATION 803

35 Eff ects of Mechanical Ventilation

on Control of Breathing 805

Dimitris Georgopoulos

36 Eff ect of Mechanical Ventilation

on Heart–Lung Interactions 821

Hernando Gomez and Michael R Pinsky

37 Eff ect of Mechanical Ventilation

on Gas Exchange 851

Roberto Rodriguez-Roisin and Antoni Ferrer

X ARTIFICIAL AIRWAYS AND MANAGEMENT 869

38 Airway Management 871

Aaron M Joff e and Steven Deem

39 Complications of Translaryngeal Intubation 895

41 Complications Associated with Mechanical Ventilation 973

Karin A Provost and Ali A El-Solh

42 Ventilator-Induced Lung Injury 995

Didier Dreyfuss, Nicolas de Prost, Jean-Damien Ricard, and Georges Saumon

VII UNCONVENTIONAL METHODS OF VENTILATOR SUPPORT 493

19 High-Frequency Ventilation 495

Alison B Froese and Niall D Ferguson

20 Extracorporeal Life Support

for Cardiopulmonary Failure 517

Heidi J Dalton and Pamela C Garcia-Filion

21 Extracorporeal Carbon Dioxide Removal 543

Antonio Pesenti, Luciano Gattinoni, and Michela Bombino

22 Transtracheal Gas Insuffl ation, Transtracheal

Oxygen Th erapy, Emergency Transtracheal

Ventilation 555

Umberto Lucangelo, Avi Nahum, and Lluis Blanch

Paolo Pelosi, Claudia Brusasco, and Marcelo Gama de Abreu

25 Independent Lung Ventilation 629

David V Tuxen

26 Mechanical Ventilation during Resuscitation 655

Holger Herff and Volker Wenzel

27 Transport of the Ventilator-Supported Patient 669

Richard D Branson, Phillip E Mason, and Jay A Johannigman

28 Home Mechanical Ventilation 683

Wolfram Windisch

29 Mechanical Ventilation in the Acute

Respiratory Distress Syndrome 699

John J Marini

30 Mechanical Ventilation for Severe Asthma 727

James W Leatherman

31 Mechanical Ventilation in Chronic

Obstructive Pulmonary Disease 741

Franco Laghi

43 Ventilator-Induced Diaphragmatic

Dysfunction 1025

Th eodoros Vassilakopoulos

44 Barotrauma and Bronchopleural Fistula 1041

Andrew M Luks and David J Pierson

45 Oxygen Toxicity 1065

Robert F Lodato

46 Pneumonia in the Ventilator-Dependent

Patient 1091

Jean E Chastre, Charles-Edouard Luyt, and Jean-Yves Fagon

47 Sinus Infections in the Ventilated Patient 1123

Jean-Jacques Rouby and Qin Lu

XII EVALUATION AND MONITORING OF VENTILATOR-SUPPORTED

PATIENTS 1137

48 Monitoring during Mechanical Ventilation 1139

Amal Jubran and Martin J Tobin

XIII MANAGEMENT OF VENTILATOR- SUPPORTED PATIENTS 1167

49 Prone Positioning in Acute

Respiratory Failure 1169

Luciano Gattinoni, Paolo Taccone, Daniele Mascheroni,

Franco Valenza, and Paolo Pelosi

50 Pain Control, Sedation, and

Neuromuscular Blockade 1183

John P Kress and Jesse B Hall

51 Humidifi cation 1199

Jean-Damien Ricard and Didier Dreyfuss

52 Airway Secretions and Suctioning 1213

Gianluigi Li Bassi

53 Fighting the Ventilator 1237

Martin J Tobin, Amal Jubran, and Franco Laghi

54 Psychological Problems in the

Ventilated Patient 1259

Yoanna Skrobik

55 Addressing Respiratory Discomfort

in the Ventilated Patient 1267

Robert B Banzett, Th omas Similowski, and Robert Brown

56 Ventilator-Supported Speech 1281

Jeannette D Hoit, Robert B Banzett, and Robert Brown

57 Sleep in the Ventilator-Supported Patient 1293

Patrick J Hanly

58 Weaning from Mechanical Ventilation 1307

Martin J Tobin and Amal Jubran

59 Extubation 1353

Martin J Tobin and Franco Laghi

60 Surfactant 1375

James F Lewis and Valeria Puntorieri

61 Nitric Oxide as an Adjunct 1389

64 Inhaled Antibiotic Th erapy 1447

Jean-Jacques Rouby, Ivan Goldstein, and Qin Lu

65 Fluid Management in the Ventilated Patient 1459

Andrew D Bersten

66 Th e Ethics of Withholding and Withdrawing Mechanical Ventilation 1473

Michael E Wilson and Elie Azoulay

67 Economics of Ventilator Care 1489

Marcelo B P Amato, MD, PhD

Associate Professor

Pulmonary

University of São Paulo

São Paulo, SP, Brazil

Division of Pulmonary, Critical Care, and Sleep Medicine

Beth Israel Deaconess Medical Center

Boston, Massachusetts

Chapter 55: Addressing Respiratory Discomfort in

the Ventilated Patient

Chapter 56: Ventilator-Supported Speech

Ahmet Baydur, MD, FACP, FCCP

Professor of Clinical Medicine

Division of Pulmonary and Critical Care Medicine

Keck School of Medicine

University of Southern California

Los Angeles, California

Chapter 32: Mechanical Ventilation in Neuromuscular Disease

Jennifer C Beck, PhD

Staff Scientist

Keenan Research Centre

Li Ka Shing Knowledge Institute of St Michael’s Hospital

Toronto, Ontario, Canada

Assistant Professor

Pediatrics

University of Toronto

Toronto, Ontario, Canada

Chapter 13: Neurally Adjusted Ventilatory Assist

Andrew D Bersten, MBBS, MD

ProfessorCritical Care MedicineFlinders University School of MedicineAdelaide, South Australia

DirectorICCUFlinders Medical CentreAdelaide, South Australia

Chapter 65: Fluid Management in the Ventilated Patient

Lluis Blanch, MD, PhD

SeniorCritical Care CenterHospital de SabadellSabadell, SpainCritical Care Center, Hospital de Sabadell, Corporació Sanitària Parc TaulíInstitut Universitari Fundació Parc Taulí-Universitat Autònoma de Barcelona

Sabadell, SpainCIBER Enfermedades Respiratorias—ISCIII, Spain

Chapter 22: Transtracheal Gas Insuffl ation, Transtracheal Oxygen

Th erapy, Emergency Transtracheal Ventilation

Michela Bombino, MD

Staff PhysicianDepartment of Perioperative Medicine and Intensive CareA.O Ospedale S Gerardo

Monza, Italy

Chapter 21: Extracorporeal Carbon Dioxide Removal

Richard D Branson, MSc, RRT

ProfessorSurgeryUniversity of CincinnatiCincinnati, OhioAdjunct FacultySchool of Aerospace MedicineWright Patterson Air Force BaseDayton, Ohio

Chapter 15: Feedback Enhancements on Conventional Ventilator Breaths

Chapter 27: Transport of the Ventilator-Supported Patient

CONTRIBUTORS

Laurent J Brochard, MD

Professor

Department of Anesthesiology, Pharmacology,

Intensive Care Medicine

University of Geneva, School of Medicine

Geneva, Switzerland

Head

Intensive Care Unit

Geneva University Hospital

Chapter 55: Addressing Respiratory Discomfort in

the Ventilated Patient

Chapter 56: Ventilator-Supported Speech

Pulmonary and Critical Care Medicine

University of North Carolina School of Medicine

Chapel Hill, North Carolina

Chapter 67: Economics of Ventilator Care

Chapter 46: Pneumonia in the Ventilator-Dependent Patient

Robert L Chatburn, MHHS, RRT-NPS, FAARC

Th e George Washington University School of MedicineWashington, District of Columbia

Director, Pulmonary, Critical Care and Respiratory ServicesMedicine

Washington Hospital CenterWashington, District of Columbia

Chapter 1: Historical Perspective on the Development of Mechanical Ventilation

Chapter 42: Ventilator-Induced Lung Injury

Steven Deem, MD

ProfessorAnesthesiology and MedicineUniversity of WashingtonSeattle, WashingtonDirector, Neurocritical CareHarborview Medical CenterSeattle, Washington

Chapter 38: Airway Management

Rajiv Dhand, MD, FCCP, FACP, FAARC

ProfessorMedicineUniversity of Tennessee Graduate School of MedicineKnoxville, Tennessee

ChairmanMedicineUniversity of Tennessee Graduate School of MedicineKnoxville, Tennessee

Chapter 63: Bronchodilator Th erapy

Anthony F DiMarco, MD

Professor

Department of Physiology & Biophysics

Case Western Reserve University

Cleveland, Ohio

Professor

MetroHealth Research Institute

MetroHealth Medical Center

Cleveland, Ohio

Chapter 62: Diaphragmatic Pacing

Didier Dreyfuss, MD

Professor

Department of Critical Care

Université Sorbonne Paris Cité and Hôpital Louis

Mourier, Colombes

Colombes, France

Chapter 42: Ventilator-Induced Lung Injury

Chapter 51: Humidifi cation

Mark W Elliott, MD, FRCP (UK)

Department of Respiratory Medicine

St James’s University Hospital

Leeds, West Yorkshire, United Kingdom

Chapter 34: Noninvasive Ventilation on a General Ward

Ali A El-Solh, MD, MPH

Professor of Medicine, Anesthesiology, and Social and

Preventive Medicine

Department of Medicine

University at Buff alo

Buff alo, New York

Director of Critical Care

VA Western New York Healthcare System

Buff alo, New York

Chapter 41: Complications Associated with Mechanical Ventilation

Jean-Yves Fagon, MD, PhD

Professor

Critical Care

Hôpiotal Européen Georges Pompidou, AP-HP

and Paris Descarte University

Toronto, Ontario, Canada

Director, Critical Care

Department of Medicine, Division of Respirology

University Health Network & Mount Sinai Hospital

Toronto, Ontario, Canada

Chapter 19: High-Frequency Ventilation

Antoni Ferrer, MD

Servei de PneumologiaHospital de SabadellCorporació Parc TaulíInstitut Universitari Fundació Parc TaulíUniversitat Autònoma de BarcelonaSabadell, Spain

Chapter 37: Eff ect of Mechanical Ventilation on Gas Exchange

Alison B Froese, MD, FRCP(C)

ProfessorDepartments of Anesthsiology and Perioperative Medicine, Pediatrics, Physiology

Queen’s UniversityKingston, Ontario, CanadaAttending PhysicianDepartment of Anesthesiology and Perioperative MedicineKingston General Hospital

Kingston, Ontario, Canada

Chapter 19: High-Frequency Ventilation

Marcelo Gama de Abreu, MD, PhD, DESA

Professor of Anesthesiology and Intensive CareDepartment of Anesthesiology and Intensive CareUniversity Hospital Carl Gustav Carus,

Dresden University of TechnologyDresden, Germany

Chapter 24: Mechanical Ventilation during General Anesthesia

Pamela C Garcia-Filion, PhD, MPH

Research ScientistCritical CarePhoenix Children’s HospitalPhoenix, Arizona

Chapter 20: Extracorporeal Life Support for Cardiopulmonary Failure

Luciano Gattinoni, MD

Full ProfessorDipartimento di Anestesiologia, Terapia Intensiva e Scienze Dermatologiche

Fondazione IRCCS CaUniversità degli Studi di MilanoMilan, Italy

Dipartimento di Anestesia, Rianimazione e Terapia del DoloreFondazione IRCCS Ca’ Granda Ospedale Maggiore PoliclinicoMilan, Italy

Chapter 21: Extracorporeal Carbon Dioxide Removal Chapter 49: Prone Positioning in Acute Respiratory Failure

Dimitris Georgopoulos, MD, PhD

ProfessorIntensive Care MedicineUniversity of Crete, Scool of MedineHeraklion, Crete

Chapter 35: Eff ects of Mechanical Ventilation on Control of Breathing

Ivan Goldstein, MD, PhD

Réanimation Chirugicale Polyvalente Pierre Viars

Hôpital Pitié-Salpêtrière

Assistance Publique Hôpitaux de Paris

Université Pierre et Marie Curie

Paris, France

Chapter 64: Inhaled Antibiotic Th erapy

Hernando Gomez, MD

Assistant Professor

Department of Critical Care Medicine

University of Pittsburgh Medical Center

Division of Intensive Care and Pulmonology

University Children’s Hospital Basel (UKBB)

Basel, Switzerland

Medical Director

Division of Intensive Care and Pulmonology

University Children’s Hospital Basel (UKBB)

Basel, Switzerland

Chapter 23: Mechanical Ventilation in the Neonatal

and Pediatric Setting

Patrick J Hanly, MD, FRCPC, MRCPI, D, ABSM

Chapter 57: Sleep in the Ventilator-Supported Patient

John E Heff ner, MD

ProfessorDepartment of MedicineOregon Health & Science UniversityPortland, Oregon

Garnjobst ChairDepartment of MedicineProvidence Portland Medical CenterPortland, Oregon

Chapter 40: Care of the Mechanically Ventilated Patient with a Tracheotomy

Holger Herff , MD

Department of Anesthesiology and Critical Care MedicineInnsbruck Medical University

Innsbruck, Austria

Chapter 26: Mechanical Ventilation during Resuscitation

Margaret Sutherland Herridge, MSc, MD, FRCPC, MPH

Associate ProfessorDepartment of MedicineUniversity of TorontoToronto, Ontario, CanadaAttending Staff Critical Care and Respiratory MedicineDepartment of Medicine

University Health NetworkToronto, Ontario, Canada

Chapter 68: Long-Term Outcomes aft er Mechanical Ventilation

Nicholas S Hill, MD

ProfessorMedicineTuft s University School of MedicineBoston, Massachussetts

ChiefDivision of Pulmonary, Critical Care and Sleep MedicineTuft s Medical Center

Rochester, Minnesota

Chapter 5: Setting the Ventilator

David L Hotchkin, MD, MSc

Chief Pulmonary & Critical Care Medicine

Internal Medicine Residency Program

Providence Portland Medical Center

Chapter 40: Care of the Mechanically

Ventilated Patient with a Tracheotomy

Department of Anesthesiology and Pain Medicine

University of Washington, Harborview Medical Center

Division of Pulmonary and Critical Care Medicine

Edward Hines Jr., Veterans Aff airs Hospital and Loyola University

of Chicago Stritch School of Medicine

Hines, Illinois

Chapter 48: Monitoring during Mechanical Ventilation

Chapter 53: Fighting the Ventilator

Chapter 58: Weaning from Mechanical Ventilation

Brian P Kavanagh, MB, FRCPC, FFARCSI (hon)

Professor & Chair

Department of Anesthesia

University of Toronto

Toronto, Canada

Staff Physician

Department of Critical Care Medicine

Hospital for Sick Children

Toronto, Canada

Chapter 14: Permissive Hypercapnia

John P Kress, MD

Associate ProfessorDepartment of Medicine, Section of Pulmonary and Critical CareUniversity of Chicago

Chicago, Illinois

Chapter 50: Pain Control, Sedation, and Neuromuscular Blockade

John G Laff ey, MD, MA, FCARCSI

ProfessorDepartment of AnesthesiaUniversity of Toronto Faculty of MedicineToronto, Ontario, Canada

Anesthetist-in-ChiefDepartment of Anestheisa

St Michael’s HospitalToronto, Ontario, Canada

Chapter 14: Permissive Hypercapnia

Franco Laghi, MD

ProfessorDivision of Pulmonary and Critical Care MedicineEdward Hines Jr Veterans Aff airs Hospital and Loyola University

of Chicago Stritch School of MedicineHines, Illinois

Chapter 4: Indications for Mechanical Ventilation Chapter 31: Mechanical Ventilation in Chronic Obstructive Pulmonary Disease

Chapter 53: Fighting the Ventilator Chapter 59: Extubation

James W Leatherman, MD

ProfessorMedicineUniversity of MinnesotaMinneapolis, MinnesotaDirector, Medical ICUPulmonary and Critical Care MedicineHennepin County Medical

Minneapolis, Minnesota

Chapter 30: Mechanical Ventilation for Severe Asthma

Francois Lellouche, MD, PhD

Associante ProfessorMedicine

Laval UniversityQuébec, QuébecCritical Care PhysicianCardiac Surgery ICUInstitut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec, Québec

Chapter 8: Pressure-Support Ventilation

Klaus Lewandowski, MD

Professor of Anesthesia and Intensive Care MedicineKlinik für Anästhesiologie, Intensivmedizin und SchmerztherapieElisabeth-Krankenhaus Essen

Essen, Germany

Chapter 61: Nitric Oxide as an Adjunct

Division of Pulmonary, Critical Care, and Sleep Medicine

Th e University of Texas Health Science Center

Houston, Texas

Chapter 45: Oxygen Toxicity

Qin Lu, MD

Multidisciplinary Intensive Care Unit Pierre Viars

Department of Anesthesiology and Critical Care Medicine

La Pitié-Salpêtrière Hospital

Assistance Publique-Hôpitaux de Paris

Université Pierre et Marie Curie

Paris, France

Chapter 47: Sinus Infections in the Ventilated Patient

Chapter 64: Inhaled Antibiotic Th erapy

Umberto Lucangelo, MD

Assistan Professor

Department of Perioperative Medicine,

Intensive Care and Emergency

University of Trieste School of Medicine

Trieste, Italy

Chapter 22: Transtracheal Gas Insuffl ation, Transtracheal Oxygen

Th erapy, Emergency Transtracheal Ventilation

Andrew M Luks, MD

Assistant Professor

Department of Medicine, Division of Pulmonary and

Critical Care Medicine

Medical Intensive Care Unit

Université Paris 6-Pierre et Marie Curie

Paris, France

Attending Physician

Medical Intensive Care Unit

Groupe Hospitalier Pitié-Salpêtrière, APHP

Paris, France

Chapter 46: Pneumonia in the Ventilator-Dependent Patient

Neil MacIntyre, MD

ProfessorMedicineDuke UniversityDurham, North Carolina

Chapter 15: Feedback Enhancements on Conventional Ventilator Breaths

Salvatore Maurizio Maggiore, MD, PhD

Assistant ProfessorDepartment of Anesthesiology and Intensive CarePoliclinico Agostino Gemelli, Università Cattolica del Sacro CuoreRome, Italy

Chapter 10: Positive End-Expiratory Pressure

Jordi Mancebo, MD

DirectorMedicina IntensivaHospital de Sant PauBarcelona, SpainAssociate ProfessorMedicine

Universitat Autònoma de BarcelonaBarcelona, Spain

Chapter 6: Assist-Control Ventilation

John J Marini, MD

Professor of MedicinePulmonary & Critical CareUniversity of MinnesotaMinneapolis/St Paul, MinnesotaDirector of Physiologic & Translational ResearchDept of Medicine

Regions Hospital

St Paul, Minnesota

Chapter 9: Pressure-Controlled and Inverse-Ratio Ventilation Chapter 29: Mechanical Ventilation in the Acute Respiratory Distress Syndrome

Chapter 27: Transport of the Ventilator-Supported Patient

Eduardo Mireles-Cabodevila, MD

Assistant ProfessorDivision of Pulmonary and Critical CareUniversity of Arkasnas for Medical SciencesLittle Rock, Arizona

Director, Medical Intensive Care UnitUniversity of Arkasnas for Medical SciencesLittle Rock, Arizona

Chapter 3: Basic Principles of Ventilator Design

Chapter 22: Transtracheal Gas Insuffl ation, Transtracheal Oxygen

Th erapy, Emergency Transtracheal Ventilation

Stefano Nava, MD

Chief

Respiratory and Critical Care

Sant’ Orsola Malpighi Hospital, University of Bologna

Bologna, Italy

Chapter 33: Chronic Ventilator Facilities

Paolo Navalesi, MD

Associate Professor

Department of Translational Medine

Università del Piemonte Orientale “A Avogadro”

Full Professor in Anesthesiology

Department of Surgical Sciences and Integrated Diagnostics

University of Genoa

Genoa, Italy

Chapter 24: Mechanical Ventilation during General Anesthesia

Chapter 49: Prone Positioning in Acute Respiratory Failure

Antonio Pesenti, MD

Professor

Department of Experimental Medicine

University of Milan Bicocca

Pulmonary and Critical Care Medicine

University of Washington School of Medicine

Seattle, Washington

Chapter 44: Barotrauma and Bronchopleural Fistula

Michael R Pinsky, MD, Dr hc, FCCP, MCCM

ProfessorDepartment of Critical Care MedicineUniversity of Pittsburgh

Pittsburgh, PhiladelphiaVice Chair for Academic Aff airsDepartment of Critical Care MedicineUniversity of Pittsburgh

Pittsburgh, Philadelphia

Chapter 36: Eff ect of Mechanical Ventilation on Heart–Lung Interactions

Karin A Provost, DO, PhD

Research Assistant ProfessorDivision of Pulmonary, Critical Care and Sleep MedicineState University of New York at Buff alo, School of Medicine and Biomedical Sciences

Buff alo, New York

Chapter 41: Complications Associated with Mechanical Ventilation

Bonn, GermanyHead of Intensive Care MedicineAnesthesiology and Intensive Care MedicineUniversity Hospital Bonn

Bonn, Germany

Chapter 11: Airway Pressure Release Ventilation

Jean-Damien Ricard, MD, PhD

ProfessorService de Réanimation Médico-chirurgicaleAssistance Publique—Hôpitaux de Paris, Hopital Louis MourierColombes, France

ResearcherUMR-S INSERM U722Université Paris DiderotParis, France

Chapter 42: Ventilator-Induced Lung Injury Chapter 51: Humidifi cation

Peter C Rimensberger, MD

Professor of Pediatrics and Intensive Care MedicineService of Neonatogy and Pediatric Intensive Care, Department of Pediatrics

University Hospital of GenevaGeneva, Switzerland

Director

Chapter 23: Mechanical Ventilation in the Neonatal and Pediatric Setting

Senior Consultant Physician

Institute of Th orax-Servei de Pneumologia

Chapter 47: Sinus Infections in the Ventilated Patient

Chapter 64: Inhaled Antibiotic Th erapy

VA Long Beach Healthcare System

Long Beach, California

Chapter 7: Intermittent Mandatory Ventilation

Georges Saumon, MD

Institut National de la Santé et de la Recherche Médicale

Faculté Xavier Bichat

Chapter 55: Addressing Respiratory Discomfort in

the Ventilated Patient

Toronto, Ontario, Canada

University of Toronto, Department of Medicine

Toronto, Ontario, Canada

Chapter 13: Neurally Adjusted Ventilatory Assist

Yoanna Skrobik, MD FRCP(C)

ProfessorDepartment of MedicineUniversité de MontréalMontréal, Québec, CanadaLise and Jean Saine Critical Care ChairCritical Care Division

Hopital Maisonneuve RosemontMontréal, Québec, Canada

Chapter 54: Psychological Problems in the Ventilated Patient

John L Stauff er, MD

Senior DirectorClinical DevelopmentFibroGen, Inc

San Francisco, CaliforniaPhysician/ConsultantMedical ServiceDepartment of Veterans Aff airsPalo Alto Health Care SystemPalo Alto, California

Chapter 39: Complications of Translaryngeal Intubation

Paolo Taccone, MD

Attending PhysicianDipartimento di Anestesia, Rianimazione (Intensiva e Subintensiva) e Terapia del Dolore

Fondazione IRCCS Cà Granda—Ospedale Maggiore PoliclinicoMilan, Italy

Chapter 49: Prone Positioning in Acute Respiratory Failure

Martin J Tobin, MD

Professor of Medicine and AnesthesiologyEdward Hines, Jr., Veterans Administration Hospital andLoyola University of Chicago Stritch School of Medicine

Editor emeritus, American Journal of Respiratory and

Critical Care Medicine

Chicago, Illinois

Chapter 4: Indications for Mechanical Ventilation Chapter 48: Monitoring during Mechanical Ventilation Chapter 53: Fighting the Ventilator

Chapter 58: Weaning from Mechanical Ventilation Chapter 59: Extubation

David V Tuxen, MBBS, FRACP, DipDHM, MD, CICM

Adjunct ProfessorDepartment of Intensive Care

Th e Alfred HospitalMelbourne, AustraliaSenior Intensivist

Chapter 25: Independent Lung Ventilation

Dipartimento di Anestesia e Rianimazione

Fondazione IRCCS Ca’ Granda—Ospedale Maggiore Policlinico

Milano, Italy

Chapter 49: Prone Positioning in Acute Respiratory Failure

Th eodoros Vassilakopoulos, MD

Associate Professor

1st Department of Critical Care and Pulmonary Services

University of Athens Medical School

Rehabilitative Respiratory Division—Weaning Unit

Fondazione Salvatore Maugeri, IRCCS

Lumezzane, Brescia, Italy

Chapter 33: Chronic Ventilator Facilities

Volker Wenzel, MD, MSc, FERC

Associate Professor and Vice ChairmanDepartment of Anesthesiology and Critical Care MedicineInnsbruck Medical University

Innsbruck, Austria

Chapter 26: Mechanical Ventilation during Resuscitation

Michael E Wilson, MD

InstructorDepartment of Internal MedicineMayo Clinic

Chapter 28: Home Mechanical Ventilation

Magdy Younes, MD, FRCP(C), PhD

Distinguished Professor EmeritusInternal Medicine

University of ManitobaWinnipeg, Manitoba, CanadaResearch Professor

Department of MedicineUniversity of CalgaryCalgary, Alberta, Canada

Chapter 12: Proportional-Assist Ventilation

More than twenty years have passed since Principles and

Practice of Mechanical Ventilation was fi rst conceived With

this third edition, the textbook has come of age When the

fi rst proposal of the book was under consideration,

review-ers thought that the corpus of knowledge pertaining to

mechanical ventilation would not be suffi cient to merit the

publication of a large tome; they opined that the contents of

such a book would require much padding Th is time around,

the challenge has been to fi t everything into a constrained

number of pages Virtually every aspect of mechanical

ven-tilation has evolved substantially over the past twenty years,

and many new areas have emerged Novel ventilator modes

have been introduced, previously discarded modes have

ac-quired a new lease of life, and long-surviving

methodolo-gies have undergone considerable refi nement Much of the

progress has stemmed from research into the mechanisms

whereby ventilators harm patients In turn, we have learned

how minor adjustments to ventilator settings can markedly

enhance patient comfort and survival A comparison of the

third and fi rst editions of Principles and Practice of

Mechani-cal Ventilation provides proof of the tremendous progress in

this fi eld during the past twenty years

Trainees hear much about the practice of medicine, as in

phrases such as clinical practice guidelines As physicians

grow older, they realize that many popular practices turn

out to be ephemeral—it is biomedical principles that remain

evergreen Mechanical ventilation remains rooted in

physi-ological principles; it is these principles that guide practice

Th e wise physician is ever mindful of the need to balance

principles with practice—to achieve the right equilibrium

between theory and pragmatic action Without a sound

knowledge of the biomedical principles that govern

ventila-tor management, a physician is reduced to setting a ventilaventila-tor

in a hit-or-miss manner or to follow a cookbook recipe With

a deep understanding of physiologic principles, a physician

is better equipped to make expert iterative adjustments to the

ventilator as a patient’s condition changes over time As with

previous editions, readers will fi nd detailed accounts of both

biomedical principles and practical advice throughout this

textbook

Electronic technology has transformed medical

publish-ing, providing rapid access to a rich store of information

Contrasted with the hours previously spent in the

periodi-cal rooms of a library, authors now retrieve pertinent

arti-cles at the click of a mouse But reading material online is not an unalloyed good Deeply engaged reading requires focused attention and commitment, whereas reading online

is accompanied by a dramatic increase in the opportunities for distraction Media do not simply act as passive channels

of communication, they also shape the process of thought Cognitive scientists have begun to uncover the diff erences between reading online and off Deep reading without dis-traction leads to the formation of rich mental connections across regions of the brain that govern such cognitive func-tions as memory and interpretation Neuroscientists expect the internet to have far-reaching eff ects on cognition and memory In contrast to a book, which is a machine for focus-ing attention and demanding the deep thinking that gener-ates memory, the internet is a machine that scatters attention and diff uses concentration Given the importance of rapid decisions in critical care medicine, which demand instant memory recall, a trainee is best advised to acquire the foun-dations for his or her storehouse of knowledge from a text-book rather than from online resources

Another advantage of a textbook is that it provides a prehensive account of a discipline in a single source, where clinicians can turn to fi nd answers to their questions about mechanical ventilation Commonly used online resources,

com-such as UpToDate, are directed toward generalists and do

not provide the depth of knowledge expected of a ist Th e information presented in medical journals is frag-mentary by design; no attempt is made to fi t published in-formation into the mosaic of existing knowledge and topics deemed unfashionable by editors are ignored Trainees who rely on bundles of reprints tend to be ignorant of the bound-aries of a subspecialty and unaware of major lacunae in their knowledge base No series of journal articles can compete with a textbook in this regard

subspecial-For a textbook to provide authoritative coverage of a fi eld, the selection of authors is crucial For each chapter, I selected scientists and clinicians who are at the forefront of research

in a given subfi eld Many of these authors undertook the seminal research that established a new area of mechanical ventilation, which was subsequently enriched and expanded

by the work of other investigators Being at the forefront

of  an area, these authors are attuned to evolving ments in a subfi eld, which makes their accounts extremely current and guards against early obsolescence of the material

develop-PREFACE

included in their chapter Each chapter has been extensively

revised; twenty-fi ve new authors provide fresh accounts of

previously covered areas; many new topics have been added;

and several chapters found in previous editions were deleted

I personally edited every line of each manuscript to ensure

reliability of the presented information and to achieve a

uni-form style throughout the book

Given that Principles and Practice of Mechanical

Ventila-tion has become one of the classics on the McGraw-Hill list,

the publisher decided to introduce color printing throughout

the new edition Th e result is a book that is not only

infor-mative but also aesthetically attractive Th e large number of

high-quality illustrations provides a pedagogical resource for

readers who are preparing slides for lectures

Th is book would not have been possible without the help

of several people, and to them I am extremely grateful First and foremost are the more than 100 authors, whose knowl-edge, commitment and wisdom form the core of the book

As with the two previous editions, I am most grateful to Amal Jubran and Franco Laghi for advice at several stages of this project I thank Lynnel Hodge for invaluable assistance

on a day-to-day basis Richard Adin copyedited the scripts with a lawyer’s eye for precision, and Brain Belval and Karen Edmondson at McGraw-Hill and Aakriti Kathuria at

manu-Th omson Digital skillfully guided the book through its duction Finally, I thank my family for their forbearance

pro-Martin J Tobin

HISTORICAL

BACKGROUND

I

CHEMISTS AND PHYSIOLOGISTS

OF THE AIR AND BLOOD

Understanding Gases

Metabolism

Blood Gases and Ventilation

EXPLORERS AND WORKING MEN

OF SUBMARINES AND BALLOONS

Exploration Under Water

Exploration in the Air

Tracheal Anesthesia Differential Pressure Translaryngeal Intubation For the Nonoperative Patient Modern Respirators

Intensive Care Adequacy of Ventilation Quality Control of Ventilators Weaning

CONCLUSION

The history of mechanical ventilation is intimately

inter-twined with the history of anatomy, chemistry, and

physi-ology; exploration under water and in the air; and of

course, modern medicine Anatomists described the

struc-tural connections of the lungs to the heart and vasculature

and developed the earliest insights into the functional

rela-tionships of these organs They emphasized the role of the

lungs in bringing air into the body and probably expelling

waste products, but showed little understanding of how air

was used by the body Chemists defined the constituents

of air and explained the metabolic processes by which the

cells used oxygen and produced carbon dioxide

Physiolo-gists complemented these studies by exploring the

rela-tionships between levels of oxygen and carbon dioxide in

the blood and ventilation Explorers tested the true limits

of physiology Travel in the air and under water exposed

humans to extremes in ventilatory demands and prompted

the development of mechanical adjuncts to ventilation

Following the various historical threads provided by the

anatomists, chemists, physiologists, and explorers provides

a useful perspective on the tapestry of a technique modern physicians accept casually: mechanical ventilation

ANATOMISTS OF THE HEART AND LUNGS

Early Greeks Early Greek physicians endorsed Empedocles’ view that all matter was composed of four essential elements: earth, air, fire, and water Each of these elements had primary qualities of heat, cold, moisture, and dryness 1 Empedocles applied this global philosophic view to the human body by stating that “innate heat,” or the soul, was distributed from the heart via the blood to various parts of the body

The Hippocratic corpus stated that the purpose of respiration was to cool the heart Air was thought to be pumped by the atria from the lungs to the right ventricle via the pulmonary artery and to the left ventricle through

the pulmonary vein 2 Aristotle believed that blood was an

indispensable part of animals but that blood was found

only in veins Arteries, in contrast, contained only air This

conclusion probably was based on his methods of

sacri-ficing animals The animals were starved, to better define

their vessels, and then strangled During strangulation,

blood pools in the right side of the heart and venous

circu-lation, leaving the left side of the heart and arteries empty 2

Aristotle described a three-chamber heart connected with

passages leading in the direction of the lung, but these

con-nections were minute and indiscernible 3 Presumably, the

lungs cooled the blood and somehow supplied it with air 4

Erasistratus (born around 300 bc ) believed that air

taken in by the lungs was transferred via the pulmonary

artery to the left ventricle Within the left ventricle, air was

transformed into pneuma zotikon , or the “vital spirit,” and

was distributed through air-filled arteries to various parts

of the body The pneuma zotikon carried to the brain was

secondarily changed to the pneuma psychikon (“animal

spirit”) This animal spirit was transmitted to the muscles

by the hollow nerves Erasistratus understood that the

right ventricle facilitated venous return by suction during

diastole and that venous valves allowed only one-way flow

of blood 1

The Greek physician Claudius Galen, practicing in

Rome around ad 161, demonstrated that arteries contain

blood by inserting a tube into the femoral artery of a dog 5 , 6

Blood flow through the tube could be controlled by

adjust-ing tension on a ligature placed around the proximal

por-tion of the artery He described a four-chamber heart with

auricles distinct from the right and left ventricles Galen

also believed that the “power of pulsation has its origin in

the heart itself ” and that the “power [to contract and dilate]

belongs by nature to the heart and is infused into the

arter-ies from it.” 5 , 6 He described valves in the heart and, as did

Erasistratus, recognized their essential importance in

pre-venting the backward discharge of blood from the heart

He alluded several times to blood flowing, for example,

from the body through the vena cava into the right

ven-tricle and even made the remarkable statement that “in

the entire body the arteries come together with the veins

and exchange air and blood through extremely fine

invis-ible orifices.” 6 Furthermore, Galen believed that “fuliginous

wastes” were somehow discharged from the blood through

the lung 6 Galen’s appreciation that the lungs supplied some

property of air to the body and discharged a waste product

from the blood was the first true insight into the lung’s role

in ventilation However, he failed in two critical ways to

appreciate the true interaction of the heart and lungs First,

he believed, as did Aristotle and other earlier Greeks, that

the left ventricle is the source of the innate heat that

vital-izes the animal Respiration in animals exists for the sake

of the heart, which requires the substance of air to cool it

Expansion of the lung caused the lightest substance, that is,

the outside air, to rush in and fill the bronchi Galen

pro-vided no insight, though, into how air, or pneuma , might

be drawn out from the bronchi and lungs into the heart

Second, he did not clearly describe the true circular nature

of blood flow from the right ventricle through the lungs and into the left ventricle and then back to the right ventri-cle His writings left the serious misconception that blood was somehow transported directly from the right to the left ventricle through the interventricular septum 1 , 5 , 6

Renaissance Physicians Byzantine and Arab scholars maintained Galen’s legacy during the Dark Ages and provided a foundation for the rebirth of science during the Renaissance 1 , 6 , 7 Around 1550, Vesalius corrected many inaccuracies in Galen’s work and even questioned Galen’s concept of blood flow from the right ventricle to the left ventricle He was skeptical about the flow of blood through the interventricular pores Galen described 1 , 6 , 8 Servetus, a fellow student of Vesalius in Paris, suggested that the vital spirit is elaborated both by the force of heat from the left ventricle and by a change in color of the blood to reddish yellow This change in color

“is generated in the lungs from a mixture of inspired air with elaborated subtle blood which the right ventricle of the heart communicates to the left This communication, however, is made not through the middle wall of the heart,

as is commonly believed, but by a very ingenious ment: the subtle blood courses through the lungs from the pulmonary artery to pulmonary vein, where it changes color During this passage the blood is mixed with inspired air and through expiration it is cleansed of its sooty vapors This mixture, suitably prepared for the production of the vital spirit, is drawn onward to the left ventricle of the heart by diastole.” 6 , 9 Although Servetus’ views proved ulti-mately to be correct, they were considered heretical at the time, and he was subsequently burned at the stake, along with most copies of his book, in 1553

Columbus, a dissectionist to Vesalius at Padua, in 1559 suggested that blood travels to the lungs via the pulmonary artery and then, along with air, is taken to the left ventri-cle through the pulmonary vein He further advanced the concept of circulation by noting that the left ventricle dis-tributes blood to the body through the aorta, blood returns

to the right ventricle in the vena cava, and venous valves in the heart allow only one-way flow 1 , 6 , 10

These views clearly influenced William Harvey, who studied anatomy with Fabricius in Padua from 1600 to

1602 Harvey set out to investigate the “true movement, pulse, action, use and usefulness of the heart and arteries.”

He questioned why the left ventricle and right ventricle traditionally were felt to play such fundamentally different roles If the right ventricle existed simply to nourish the lungs, why was its structure so similar to that of the left ventricle? Furthermore, when one directly observed the beating heart in animals, it was clear that the function of both right and left ventricles also was similar In both cases, when the ventricle contracted, it expelled blood, and when

it relaxed, it received blood Cardiac systole coincided with

arterial pulsations The motion of the auricles preceded

that of the ventricles Indeed, the motions are

consecu-tive with a rhythm about them, the auricles contracting

and forcing blood into the ventricles and the ventricles,

in turn, contracting and forcing blood into the arteries

“Since blood is constantly sent from the right ventricle

into the lungs through the pulmonary artery and likewise

constantly is drawn the left ventricle from the lungs…it

cannot do otherwise than flow through continuously This

flow must occur by way of tiny pores and vascular

open-ings through the lungs Thus, the right ventricle may be

said to be made for the sake of transmitting blood through

the lungs, not for nourishing them.” 6 , 11

Harvey described blood flow through the body as being

circular This was easily understood if one considered

the quantity of blood pumped by the heart If the heart

pumped 1 to 2 drams of blood per beat and beat 1000 times

per half-hour, it put out almost 2000 drams in this short

time This was more blood than was contained in the whole

body Clearly, the body could not produce amounts of

blood fast enough to supply these needs Where else could

all the blood go but around and around “like a stage army

in an opera.” If this theory were correct, Harvey went on to

say, then blood must be only a carrier of critical nutrients

for the body Presumably, the problem of the elimination

of waste vapors from the lungs also was explained by the

idea of blood as the carrier 1 , 6 , 11

With Harvey’s remarkable insights, the relationship

between the lungs and the heart and the role of blood were

finally understood Only two steps remained for the

anat-omists to resolve First, the nature of the tiny pores and

vascular openings through the lungs had to be explained

About 1650, Malpighi, working with early microscopes,

found that air passes via the trachea and bronchi into

and out of microscopic saccules with no clear

connec-tion to the bloodstream He further described capillaries:

“… and such is the wandering about of these vessels as

they proceed on this side from the vein and on the other

side from the artery, that the vessels no longer maintain a

straight direction, but there appears a network made up

of the articulations of the two vessels…blood flowed away

along [these] tortuous vessels … always contained within

tubules.” 1 , 6 Second, Borelli, a mathematician in Pisa and a

friend of Malpighi, suggested the concept of diffusion Air

dissolved in liquids could pass through membranes

with-out pores Air and blood finally had been linked in a

plau-sible manner 1

CHEMISTS AND PHYSIOLOGISTS

OF THE AIR AND BLOOD

Understanding Gases

The anatomists had identified an entirely new set of

prob-lems for chemists and physiologists to consider The right

ventricle pumped blood through the pulmonary artery to

the lungs In the lungs the blood took up some substance, evidenced by the change in color observed as blood passes through the pulmonary circulation Presumably the blood released “fuliginous wastes” into the lung The site of this exchange was thought to be at the alveolar–capillary inter-face, and it probably occurred by the process of diffusion What were the substances exchanged between blood and air in the lung? What changed the color of blood and was essential for the production of the “innate heat”? What was the process by which “innate heat” was produced, and where did this combustion occur, in the left ventricle as supposed from the earliest Greek physician-philosophers

or elsewhere? Where were the “fuliginous wastes” duced, and were they in any way related to the production

pro-of “innate heat”? If blood were a carrier, pumped by the left ventricle to the body, what was it carrying to the tissues and then again back to the heart?

Von Helmont, about 1620, added acid to limestone and potash and collected the “air” liberated by the chemi-cal reaction This “air” extinguished a flame and seemed

to be similar to the gas produced by fermentation This

“air” also appeared to be the same gas as that found in the Grotto del Cane This grotto was notorious for containing air that would kill dogs but spare their taller masters 1 The gas, of course, was carbon dioxide In the late seventeenth century, Boyle recognized that there is some substance in air that is necessary to keep a flame burning and an animal alive Place a flame in a bell jar, and the flame eventually will go out Place an animal in such a chamber, and the animal eventually will die If another animal is placed in that same chamber soon thereafter, it will die suddenly Mayow showed, around 1670, that enclosing a mouse in

a bell jar resulted eventually in the mouse’s death If the bell jar were covered by a moistened bladder, the bladder bulged inward when the mouse died Obviously, the ani-mals needed something in air for survival Mayow called this the “nitro-aereal spirit,” and when it was depleted, the animals died 1 , 12 This gas proved to be oxygen Boyle’s sus-picions that air had other qualities primarily owing to its ingredients seemed well founded 13 , 14

In a remarkable and probably entirely intuitive insight, Mayow suggested that the ingredient essential for life, the

“nitro-aereal spirit,” was taken up by the blood and formed the basis of muscular contraction Evidence supporting this concept came indirectly In the early 1600s, the concept of air pressure was first understood von Guericke invented

a pneumatic machine that reduced air pressure 1 , 15 Robert Boyle later devised the pneumatic pump that could extract air from a closed vessel to produce something approaching

a vacuum ( Fig 1-1 ) Boyle and Hooke used this pneumatic engine to study animals under low-pressure conditions Apparently Hooke favored dramatic experiments, and he often demonstrated in front of crowds that small animals died after air was evacuated from the chamber Hooke actu-ally built a human-sized chamber in 1671 and volunteered

to enter it Fortunately, the pump effectively removed only about a quarter of the air, and Hooke survived 16 Boyle

believed that the difficulty encountered in breathing under

these conditions was caused solely by the loss of

elastic-ity in the air He went on to observe, however, that animal

blood bubbled when placed in a vacuum This observation

clearly showed that blood contained a gas of some type 13 , 14

In 1727, Hales introduced the pneumatic trough ( Fig 1-2 )

With this device he was able to distinguish between free

gas and gas no longer in its elastic state but combined

with a liquid 1 The basis for blood gas machines had been

invented

The first constituent of air to be truly recognized was

carbon dioxide Joseph Black, around 1754, found that

limestone was transformed into caustic lime and lost weight

on being heated The weight loss occurred because a gas

was liberated during the heating process The same results

occurred when the carbonates of alkali metals were treated

with an acid such as hydrochloric acid He called the

lib-erated gas “fixed air” and found that it would react with

lime water to form a white insoluble precipitate of chalk

FIGURE 1-1 A pneumatical engine, or vacuum pump, devised by

Hooke in collaboration with Boyle around 1660 The jar ( 6 ) contains

an animal in this illustration Pressure is lowered in the jar by raising

the tightly fitting slide ( 5 ) with the crank ( 4 ) (Used, with permission,

from Graubard 6 )

FIGURE 1-2 In 1727, Hales developed the pneumatic trough, shown

on the bottom of this illustration This device enabled him to collect gases produced by heating On the top is a closed-circuit respiratory apparatus for inhaling the collected gases (Used, with permission, from Perkins 1 )

This reaction became an invaluable marker for the ence of “fixed air.” Black subsequently found that “fixed air” was produced by burning charcoal and fermenting beer In

pres-a rempres-arkpres-able experiment he showed thpres-at “fixed pres-air” wpres-as given off by respiration In a Scottish church where a large congregation gathered for religious devotions, he allowed lime water to drip over rags in the air ducts After the ser-vice, which lasted about 10 hours, he found a precipitate of crystalline lime (CaCO 3 ) in the rags, proof that “fixed air” was produced during the services Black recognized that

“fixed air” was the same gas described by von Helmont that would extinguish flame and life 1 , 4 , 14

In the early 1770s, Priestley and Scheele, working pendently of each other, both produced and isolated “pure

inde-air.” Priestley used a 12-inch lens to heat mercuric oxide

The gas released in this process passed through the long

neck of a flask and was isolated over mercury This gas

allowed a flame to burn brighter and a mouse to live

lon-ger than in ordinary air 1 , 4 , 15 Scheele also heated chemicals

such as mercuric oxide and collected the gases in ox or

hog bladders Like Priestley, Scheele found that the gas

iso-lated made a flame burn brighter This gas was the

“nitro-aereal spirit” described by Mayow Priestley and Scheele

described their observations to Antoine Lavoisier He

repeated Priestley’s experiments and found that if mercuric

oxide was heated in the presence of charcoal, Black’s “fixed

air” would be produced Further work led Lavoisier to the

conclusion that ordinary air must have at least two

sepa-rate components One part was respirable, combined with

metals during heating, and supported combustion The

other part was nonrespirable In 1779, Lavoisier called the

respirable component of air “oxygen.” He also concluded

from his experiments that “fixed air” was a combination

of coal and the respirable portion of air Lavoisier realized

that oxygen was the explanation for combustion 1 , 4 , 17

Metabolism

In the 1780s, Lavoisier performed a brilliant series of

stud-ies with the French mathematician Laplace on the use of

oxygen by animals Lavoisier knew that oxygen was

essen-tial for combustion and necessary for life Furthermore, he

was well aware of the Greek concept of internal heat

pre-sumably produced by the left ventricle The obvious

ques-tion was whether animals used oxygen for some type of

internal combustion Would this internal combustion be

similar to that readily perceived by the burning of coal?

To answer this question, the two great scientists built an

ice calorimeter ( Fig 1-3 ) This device could do two things

Because the melting ice consumed heat, the rate at which

ice melted in the calorimeter could be used as a

quantita-tive measure of heat production within the calorimeter In

addition, the consumption of oxygen could be measured

It then was a relatively simple task to put an animal inside

the calorimeter and carefully measure heat production

and oxygen consumption As Lavoisier suspected, the

amount of heat generated by the animal was similar to

that produced by burning coal for the quantity of oxygen

consumed 1 , 4

The Greeks suspected that the left ventricle produced

innate heat, and Lavoisier himself may have thought that

internal combustion occurred in the lungs 4 Spallanzani,

though, took a variety of tissues from freshly killed animals

and found that they took up oxygen and released carbon

dioxide 1 Magnus, relying on improved methods of

analyz-ing the gas content of blood, found higher oxygen levels

in arterial blood than in venous blood but higher carbon

dioxide levels in venous blood than in arterial blood He

believed that inhaled oxygen was absorbed into the blood,

transported throughout the body, given off at the capillary

FIGURE 1-3 The ice calorimeter, designed by Lavoisier and Laplace, allowed these French scientists to measure the oxygen consumed by an animal and the heat produced by that same animal With careful mea- surements, the internal combustion of animals was found to be similar,

in terms of oxygen consumption and heat production, to open fires (Used, with permission, from Perkins 1 )

level to the tissues, and there formed the basis for the mation of carbon dioxide 18 In 1849, Regnault and Reiset perfected a closed-circuit metabolic chamber with devices for circulating air, absorbing carbon dioxide, and periodi-cally adding oxygen ( Fig 1-4 ) Pettenkofer built a closed-circuit metabolic chamber large enough for a man and

for-a bicycle ergometer ( Fig 1-5 ) 19 This device had a steam engine to pump air, gas meters to measure air volumes, and barium hydroxide to collect carbon dioxide Although these devices were intended to examine the relationship between inhaled oxygen and exhaled carbon dioxide, they also could be viewed as among some of the earliest meth-ods of controlled ventilation

Blood Gases and Ventilation

In separate experiments, the British scientist Lower and the Irish scientist Boyle provided the first evidence that uptake of gases in the lungs was related to gas content in the blood In 1669, Lower placed a cork in the trachea of

an animal and found that arterial blood took on a venous appearance Removing the cork and ventilating the lungs with a bellows made the arterial blood bright red again Lower felt that the blood must take in air during its course through the lungs and therefore owed its bright color entirely to an admixture of air Moreover, after the air had

FIGURE 1-4 Regnault and Reiset developed a closed-circuit metabolic chamber in 1849 for studying gen consumption and carbon dioxide production in animals (Used, with permission, from Perkins 1 )

FIGURE 1-5 A This huge device, constructed by Pettenkoffer, was

large enough for a person B The actual chamber The gas meters used

to measure gas volumes are shown next to the chamber The steam

engine and gasometers for circulating air are labeled A C A close-up

view of the gas-absorbing device adjacent to the gas meter in B With

this device Pettenkoffer and Voit studied the effect of diet on the

respi-ratory quotient (Used, with permission, from Perkins 1 )

B

C A

in large measure left the blood again in the viscera, the

venous blood became dark red 20 A year later Boyle showed

with his vacuum pump that blood contained gas

Follow-ing Lavoisier’s studies, scientists knew that oxygen was the

component of air essential for life and that carbon dioxide

was the “fuliginous waste.”

About 1797, Davey measured the amount of oxygen

and carbon dioxide extracted from blood by an air pump 4

Magnus, in 1837, built a mercurial blood pump for

quan-titative analysis of blood oxygen and carbon dioxide

con-tent 18 Blood was enclosed in a glass tube in continuity

with a vacuum pump Carbon dioxide extracted by means

of the vacuum was quantified by the change in weight of

carbon dioxide–absorbent caustic potash Oxygen content

was determined by detonating the gas in hydrogen 15 A

limiting factor in Magnus’s work was the assumption that

the quantity of oxygen and carbon dioxide in blood simply

depended on absorption Hence, the variables determining

gas content in blood were presumed to be the absorption

coefficients and partial pressures of the gases In the 1860s,

Meyer and Fernet showed that the gas content of blood was

determined by more than just simple physical properties

Meyer found that the oxygen content of blood remained

relatively stable despite large fluctuations in its partial

pressure 21 Fernet showed that blood absorbed more

oxy-gen than did saline solution at a given partial pressure 15

Paul Bert proposed that oxygen consumption could

not strictly depend on the physical properties of oxygen

dissolving under pressure in the blood As an example,

he posed the problem of a bird in flight changing altitude

abruptly Oxygen consumption could be maintained with

the sudden changes in pressure only if chemical reactions

contributed to the oxygen-carrying capacity of blood 15

In 1878, Bert described the curvilinear oxygen

dissocia-tion curves relating oxygen content of blood to its

pres-sure Hoppe-Seyler was instrumental in attributing the

oxygen-carrying capacity of the blood to hemoglobin 22

Besides his extensive experiments with animals in either

high- or low-pressure chambers, Bert also examined the

effect of ventilation on blood gas levels Using a bellows

to artificially ventilate animals through a tracheostomy, he

found that increasing ventilation would increase oxygen

content in blood and decrease the carbon dioxide content

Decreasing ventilation had the opposite effect 15 Dohman,

in Pflüger’s laboratory, showed that both carbon dioxide

excess and lack of oxygen would stimulate ventilation 23

In 1885, Miescher-Rusch demonstrated that carbon

diox-ide excess was the more potent stimulus for ventilation 1

Haldane and Priestley, building on this work, made great

strides in analyzing the chemical control of ventilation

They developed a device for sampling end-tidal, or

alveo-lar exhaled, gas ( Fig 1-6 ) Even small changes in alveoalveo-lar

carbon dioxide fraction greatly increased minute

ventila-tion, but hypoxia did not increase minute ventilation until

the alveolar oxygen fraction fell to 12% to 13% 24

Early measurements of arterial oxygen and carbon

diox-ide tensions led to wdiox-idely divergent results In Ludwig’s

FIGURE 1-6 This relatively simple device enabled Haldane and Priestley to collect end-tidal expired air, which they felt approximated alveolar air The subject exhaled through the mouthpiece at the right

At the end of expiration, the stopcock on the accessory collecting bag was opened, and a small aliquot of air was trapped in this device

(Used, with permission, from Best CH, Taylor NB, Physiological Basis of Medical Practice Baltimore, MD: Williams & Wilkins; 1939:509.)

laboratory the arterial partial pressure of oxygen was thought to be approximately 20 mm Hg The partial pres-sure of carbon dioxide reportedly was much higher These results could not entirely support the concept of passive gas movement between lung blood and tissues based on pressure gradients Ludwig and others suspected that an active secretory process was involved in gas transport 4 Coincidentally, the French biologist Biot observed that some deep-water fish had extremely large swim bladders The gas composition in those swim bladders seemed to

be different than that of atmospheric air Biot concluded that gas was actively secreted into these bladders 4 , 15 , 24 , 25 Pflüger and his coworkers developed the aerotonometer, a far more accurate device for measuring gas tensions than that used by Ludwig When they obstructed a bronchus, they found no difference in the gas composition of air distal to the bronchial obstruction and that of pulmonary venous blood draining the area They concluded that the lung did not rely on active processes for transporting oxy-gen and carbon dioxide; passive diffusion was a sufficient explanation 26

Although Pflüger’s findings were fairly convincing at the time, Bohr resurrected this controversy 27 He found greater variability in blood and air carbon dioxide and oxygen ten-sions than previously reported by Pflüger and suspected that under some circumstances secretion of gases might occur In response, Krogh, a student of Bohr’s, developed

an improved blood gas–measuring technique relying on the microaerotonometer ( Fig 1-7 ) With his wife, Krogh convincingly showed that alveolar air oxygen tension was higher than blood oxygen tension and vice versa for carbon dioxide tensions, even when the composition of inspired air was varied 28 Douglas and Haldane confirmed Krogh’s findings but wondered whether they were appli-cable only to people at rest Perhaps during the stress of either exercise or high-altitude exposure, passive diffusion might not be sufficient Indeed, the ability to secrete oxy-gen might explain the tolerance to high altitude developed

by repeated or chronic exposures Possibly carbon ide excretion might occur with increased carbon dioxide

diox-levels 26 In a classic series of experiments, Marie Krogh

showed that diffusion increased with exercise secondary to

the concomitant increase in cardiac output 29 Barcroft put

to rest the diffusion-versus-secretion controversy with his

“glass chamber” experiment For 6 days he remained in a

closed chamber subjected to hypoxia similar to that found

on Pike’s Peak Oxygen saturation of radial artery blood

was always less than that of blood exposed to

simultane-ously obtained alveolar gas, even during exercise These

were expected findings for gas transport based simply on

passive diffusion 30

With this body of work, the chemists and

physiolo-gists had provided the fundamental knowledge necessary

for the development of mechanical ventilation Oxygen

was the component of atmospheric gas understood to be

essential for life Carbon dioxide was the “fuliginous waste”

3

C

FIGURE 1-7 Krogh’s microaerotonometer A An enlarged view of the

lower part of B Through the bottom of the narrow tube ( 1 ) in A , blood

is introduced The blood leaves the upper end of the narrow tube ( 1 ) in

a fine jet and plays on the air bubble ( 2 ) Once equilibrium is reached

between the air bubble and blood, the air bubble is drawn by the screw

plunger ( 4 ) into the graduated capillary tube shown in B The volume

of the air bubble is measured before and after treatment with KOH to

absorb CO 2 and potassium pyrogallate to absorb O 2 The changes in

volume of the bubble reflect blood CO 2 and O 2 content C A model of

A designed for direct connection to a blood vessel (Used, with

permis-sion, from Best CH, Taylor NB, Physiological Basis of Medical Practice

Baltimore, MD: Williams & Wilkins; 1939:521.)

gas released from the lungs The exchange of oxygen and carbon dioxide between air and blood was determined by the tensions of these gases and simple passive diffusion Blood was a carrier of these two gases, as Harvey first sug-gested Oxygen was carried in two ways, both dissolved in plasma and chemically combined with hemoglobin Blood carried oxygen to the tissues, where oxygen was used in cellular metabolism, that is, the production of the body’s

“innate heat.” Carbon dioxide was the waste product of this reaction Oxygen and carbon dioxide tensions in the blood were related to ventilation in two critical ways Increasing ventilation would secondarily increase oxygen tensions and decrease carbon dioxide levels Decreasing ventilation would have the opposite effect Because blood levels of oxygen and carbon dioxide could be measured, physiologists now could assess the adequacy of ventila-tion Decreased oxygen tensions and increased carbon dioxide tensions played a critical role in the chemical con-trol of ventilation

It was not understood, though, how carbon dioxide was carried by the blood until experiments performed by Bohr 31 and Haldane 32 The concept of blood acid–base activity was just beginning to be examined in the early 1900s By the 1930s, a practical electrode became available for determin-ing anaerobic blood pH, 33 but pH was not thought to be useful clinically until the 1950s In 1952, during the polio epidemic in Copenhagen, Ibsen suggested that hypoven-tilation, hypercapnia, and respiratory acidosis caused the high mortality rate in polio patients with respiratory paralysis Clinicians disagreed because high blood levels

of “bicarbonate” indicated an alkalosis By measuring pH, Ibsen was proved correct, and clinicians became acutely aware of the importance of determining both carbon diox-ide levels and pH 4 Numerous workers looked carefully at such factors as base excess, duration of hypercapnia, and renal buffering activity before Siggaard-Anderson pub-lished a pH/log PCO2 acid–base chart in 1971 34 This chart proved to be an invaluable basis for evaluating acute and chronic respiratory and metabolic acid–base disturbances The development of practical blood gas machines suitable for use in clinical medicine did not occur until electrodes became available for measuring oxygen and carbon diox-ide tensions in liquid solutions Stow built the first elec-trode capable of measuring blood PCO2 As the basis for this device, he used a glass pH electrode with a coaxial central calomel electrode opening at its tip A unique adaptation, however, was the use of a rubber finger cot to wrap the electrode This wrap trapped a film of distilled water over the electrode The finger cot then acted as a semiperme-able membrane to separate the measuring electrode from the sample 35 Clark used a similar idea in the development

of an oxygen measuring device Platinum electrodes were used as the measuring device, and polyethylene served as the semipermeable membrane 36 By 1973, Radiometer was able to commercially produce the first automated blood gas analyzer, the ABL, capable of measuring PO2, PCO2, and

pH in blood 4

EXPLORERS AND WORKING MEN

OF SUBMARINES AND BALLOONS

Travel in the deep sea and flight have intrigued humankind

for centuries Achieving these goals has followed a typical

pattern First, individual explorers tested the limits of human

endurance As mechanical devices were developed to extend

those limits, the deep sea and the air became accessible to

commercial and military exploration These forces further

intensified the need for safe and efficient underwater and

high-altitude travel Unfortunately, the development of

vehi-cles to carry humans aloft and under water proceeded faster

than the appreciation of the physiologic risks Calamitous

events ensued, with serious injury and death often a

conse-quence Only a clear understanding of the ventilatory

prob-lems associated with flight and deep-sea travel has enabled

human beings to reach outer space and the depths of the

ocean floor

Exploration Under Water

Diving bells undoubtedly were derived from ancient

humans’ inverting a clay pot over their heads and

breath-ing the trapped air while under water These devices were

used in various forms by Alexander the Great at the siege

of Tyre in 332 bc , the Romans in numerous naval battles,

and pirates in the Black Sea 37 , 38 In the 1500s, Sturmius

con-structed a heavy bell that, even though full of air, sank of its

own weight When the bell was positioned at the bottom of

fairly shallow bodies of water, workers were able to enter and

work within the protected area Unfortunately, these bells

had to be raised periodically to the surface to refresh the air

Although the nature of the foul air was not understood, an

important principle of underwater work, the absolute need

for adequate ventilation, was appreciated 15

Halley devised the first modern version of the diving bell

in 1690 ( Fig 1-8 ) To drive out the air accumulated in the bell

and “made foul” by the workers’ respiration, small barrels of

air were let down periodically from the surface and opened

within the bell Old air was released through the top of the

bell by a valve In 1691, Papin developed a technique for

con-stantly injecting fresh air from the surface directly into the

bell by means of a strong leather bellows In 1788, Smeaton

replaced the bellows with a pump for supplying fresh air to

the submerged bell 15 , 37 , 38

Techniques used to make diving bells practical also were

applied to divers Xerxes used them to recover sunken

trea-sure 39 Sponge divers in the Mediterranean in the 1860s could

stay submerged for 2 to 4 minutes and reach depths of 45

to 55 m 40 Amas, female Japanese divers using only goggles

and a weight to facilitate rapid descent, made dives to similar

depths 41 Despite the remarkable adaptations of

breath-hold-ing measures developed by these naked divers, 42 the

commer-cial and military use of naked divers was limited In 77 ad ,

Pliny described divers breathing through tubes while

sub-merged and engaged in warfare More sophisticated diving

suits with breathing tubes were described by Leonardo da Vinci in 1500 and Renatus in 1511 Although these breathing tubes prolonged underwater activities, they did not enable divers to reach even moderate depths 15 Borelli described a complete diving dress with tubes in the helmet for recirculat-ing and purifying air in 1680 ( Fig 1-9 ) 37

Klingert described the first modern diving suit in 1797 37

It consisted of a large helmet connected by twin breathing pipes to an air reservoir that was large enough to have an associated platform The diver stood on the platform and inhaled from the air reservoir through an intake pipe on the top of the reservoir and exhaled through a tube con-nected to the bottom of the reservoir Siebe made the first commercially viable diving dress The diver wore a metal helmet riveted to a flexible waterproof jacket This jacket extended to the diver’s waist but was not sealed Air under pressure was pumped from the surface into the diver’s hel-met and escaped through the lower end of the jacket In

1837, Siebe modified this diving dress by extending the jacket to cover the whole body The suit was watertight at the wrists and ankles Air under pressure entered the suit through a one-way valve at the back of the helmet and was released from the suit by an adjustable valve at the side of the helmet ( Fig 1-10 ) 37 In 1866, Denayouze incorporated

a metal air reservoir on the back of the diver’s suit Air was pumped directly into the reservoir, and escape of air from the suit was adjusted by the diver 15

Siebe, Gorman, and Company produced the first cal self-contained diving dress in 1878 This suit had a cop-per chamber containing potash for absorbing carbon dioxide and a cylinder of oxygen under pressure 37 Fleuss cleverly revised this diving suit in 1879 to include an oronasal mask with an inlet and an exhaust valve The inlet valve allowed inspiration from a metal chamber containing oxygen under pressure Expiration through the exhaust valve was directed into metal chambers under a breastplate that contained car-bon dioxide absorbents Construction of this appliance was

practi-so precise that Fleuss used it not only to stay under water for hours but also to enter chambers containing noxious gases The Fleuss appliance was adapted rapidly and successfully to mine rescue work, where explosions and toxic gases previ-ously had prevented such efforts 43

As Siebe, Gorman, and Company successfully marketed diving suits, commercial divers began to dive deeper and longer Unfortunately, complications developed for two separate reasons Decompression illness was recognized first In 1830, Lord Cochrane took out a patent in England for “an apparatus for compressing atmospheric air within the interior capacity of subterraneous excavations [to]…counteract the tendency of superincumbent water to flow

by gravitation into such excavations…and which tus at the same time is adapted to allowing workmen to carry out their ordinary operations of excavating, sinking, and mining.” 38 In 1841, Triger described the first practi-cally applied caisson for penetrating the quicksands of the Loire River ( Fig 1-11 ) 44 This caisson, or hollow iron tube, was sunk to a depth of 20 m The air within the caisson was

appara-compressed by a pump at the surface The high air pressure

within the caisson was sufficient to keep water out of the

tube and allow workers to excavate the bottom Once the

excavation reached the prescribed depth, the caisson was

filled with cement, providing a firm foundation During the

excavation process, workers entered and exited the caisson

through an airlock During this work, Triger described the first cases of “caisson disease,” or decompression illness,

in workers after they had left the pressurized caisson As this new technology was applied increasingly in shaft and tunnel work (e.g., the Douchy mines in France in 1846; bridges across the Midway and Tamar rivers in England in

FIGURE 1-8 Halley’s version of the diving bell Small barrels of fresh air were lowered periodically to the bell, and the worker inside the bell released the air “Foul air” often was released by way of a valve at the top of the bell Workers could exit the bell for short periods (Used, with permission, from Hill 38 )

FIGURE 1-9 A fanciful diving suit designed by Borelli in 1680 (Used,

with permission, from Hill 38 )

1851 and 1855, respectively; and the Brooklyn Bridge,

con-structed between 1870 and 1873), caisson disease was

rec-ognized more frequently Bert was especially instrumental

in pointing out the dangers of high pressure 15 Denayouze

supervised many commercial divers and probably was

among the first to recognize that decompression caused

illness in these divers 15 In the early 1900s, Haldane

devel-oped safe and acceptable techniques for staged

decompres-sion based on physiologic principles 38

Haldane also played a critical role in examining how well

Siebe’s closed diving suit supplied the ventilation needs of

divers This work may have been prompted by Bert’s

stud-ies with animals placed in high-pressure chambers Bert

found that death invariably occurred when inspired

car-bon dioxide levels reached a certain threshold Carcar-bon

dioxide absorbents placed in the high-pressure chamber

prevented deaths 15 Haldane’s studies in this area were

encouraged by a British Admiralty committee studying the

risks of deep diving in 1906 Haldane understood that

min-ute ventilation varied directly with alveolar carbon dioxide

levels It appeared reasonable that the same minute

ventila-tion needed to maintain an appropriate PACO2 at sea level

would be needed to maintain a similar PACO2 under water

What was not appreciated initially was that as the diver

descended and pressure increased, pump ventilation at the surface necessarily also would have to increase to maintain minute ventilation Haldane realized that at 2 atmospheres

of pressure, or 33 ft under water, pump ventilation would have to double to ensure appropriate ventilation This does

FIGURE 1-10 A The metal helmet devised by Siebe is still used today

B The complete diving suit produced by Siebe, Gorman, and Company

in the nineteenth century included the metal helmet, a diving dress sealed at the wrists and ankles, and weighted shoes (Used, with per- mission, from Hill 38 )

A

B

not take into account muscular effort, which would further

increase ventilatory demands Unfortunately, early divers

did not appreciate the need to adjust ventilation to the

diving suit Furthermore, air pumps often leaked or were

maintained inadequately Haldane demonstrated the

rela-tionship between divers’ symptoms and hypercapnia by

collecting exhaled gas from divers at various depths The

fraction of carbon dioxide in the divers’ helmets ranged

from 0.0018 to 0.10 atm 26 , 38 The investigations of Bert and

Haldane finally clarified the nature of “foul air” in

div-ing bells and suits and the role of adequate ventilation in

protecting underwater workers from hypercapnia Besides

his work with divers, Haldane also demonstrated that the

“black damp” found in mines actually was a dangerously

toxic blend of 10% CO 2 and 1.45% O 2 45 He developed a

self-contained rescue apparatus for use in mine

acci-dents that apparently was more successful than the Fleuss

appliance 46

Diving boats were fancifully described by Marsenius,

in 1638, and others Only the boat designed by Debrell in

1648 appeared plausible because “besides the mechanical

FIGURE 1-11 The caisson is a complex device enabling workers to

function in dry conditions under shallow bodies of water or in other

potentially flooded circumstances A tube composed of concentric

rings opens at the bottom to a widened chamber, where workers can

be seen At the top of the tube is a blowing chamber for maintaining

air pressure and dry conditions within the tube Workers enter at the

top through an air lock and gain access to the working area via a ladder

through the middle of the tube (Used, with permission, from Hill 38 )

contrivances of his boat, he had a chemical liquor, the fumes

of which, when the vessel containing it was unstopped, would speedily restore to the air, fouled by the respiration, such a portion of vital spirits as would make it again fit for that office.” Although the liquor was never identified, it undoubtedly was an alkali for absorbing carbon dioxide 38 Payerne built a submarine for underwater excavation in

1844 Since 1850, the modern submarine has been oped primarily for military actions at sea

Submarines are an intriguing physiologic experiment

in simultaneously ventilating many subjects Ventilation in submarines is complex because it involves not only oxygen and carbon dioxide levels but also heat, humidity, and body odors Early work in submarines documented substantial increases in temperature, humidity, and carbon dioxide levels 47 Mechanical devices for absorption of carbon diox-ide and air renewal were developed quickly, 48 and by 1928,

Du Bois thought that submarines could remain submerged safely for up to 96 hours 49 With the available carbon diox-ide absorbents, such as caustic soda, caustic potash, and soda lime, carbon dioxide levels could be kept within relatively safe levels of less than 3% Supplemental oxygen carried by the submarine could maintain a preferred frac-tional inspired oxygen concentration above 17% 39 , 50 – 52 Exploration in the Air

In 1782, the Montgolfier brothers astounded the world by constructing a linen balloon about 18 m in diameter, filling

it with hot air, and letting it rise about 2000 m into the air

On November 21, 1783, two Frenchmen, de Rozier and the Marquis d’Arlandes, were the first humans to fly in a Mont-golfier balloon 53 Within a few years, Jeffreys and Blanchard had crossed the English Channel in a balloon, and Charles had reached the astonishing height of 13,000 ft in a hydro-gen-filled balloon As with diving, however, the machines that carried them aloft brought human passengers past the limits of their physiologic endurance Glaisher and Coxwell reached possibly 29,000 ft in 1862, but suffered temporary paralysis and loss of consciousness 4 , 26 , 54

Acoste’s description in 1573 of vomiting, disequilibrium, fatigue, and distressing grief as he traversed the Escaleras (Stairs) de Pariacaca, between Cuzco and Lima, Peru (“one

of the highest places in the universe”), was widely known

in Europe 55 In 1804, von Humboldt attributed these high altitude symptoms to a lack of oxygen Surprisingly, how-ever, he found that the fraction of inspired oxygen in high-altitude air was similar to that found in sea-level air He actually suggested that respiratory air might be used to pre-vent mountain sickness 56 Longet expanded on this idea in

1857 by suggesting that the blood of high-altitude dwellers should have a lower oxygen content than that of sea-level natives In a remarkable series of observations during the 1860s, Coindet described respiratory patterns of French people living at high altitude in Mexico City Compared with sea-level values, respirations were deeper and more

frequent, and the quantity of air expired in 1 minute was

somewhat increased He felt that “this is logical since the

air of altitudes contains in a given volume less oxygen at

a lower barometric pressure…[and therefore] a greater

quantity of this air must be absorbed to compensate for

the difference.” 15 Although these conclusions might seem

reasonable now, physiologists of the time also considered

decreased air elasticity, wind currents, exhalations from

harmful plants, expansion of intestinal gas, and lack of

support in blood vessels as other possible explanations

for the breathing problems experienced at high altitude

Bert, the father of aviation medicine, was instrumental in

clarifying the interrelationship among barometric

pres-sure, oxygen tension, and symptoms In experiments on

animals exposed to low-pressure conditions in

cham-bers ( Fig 1-12 ), carbonic acid levels increased within the

chamber, but carbon dioxide absorbents did not prevent

death Supplemental oxygen, however, protected animals

from dying under simulated high-altitude conditions

( Fig 1-13 ) More importantly, he recognized that death

occurred as a result of the interaction of both the fraction

of inspired oxygen and barometric pressure When a

mul-tiple of these two variables—that is, the partial pressure

of oxygen—reached a critical threshold, death ensued 15 , 39

Croce-Spinelli, Sivel, and Tissandier were

adventur-ous French balloonists eager to reach the record height of

8000 m At Bert’s urging, they experimented with the use

of oxygen tanks in preliminary balloon flights and even in Bert’s decompression chamber In 1875, they began their historic attempt to set an altitude record supplied with oxygen cylinders ( Fig 1-14 ) Unfortunately, at 24,600 ft they released too much ballast, and their balloon ascended

so rapidly that they were stricken unconscious before they could use the oxygen When the balloon eventually returned to earth, only Tissandier remained alive 4 , 54 This tragedy shook France The idea that two men had died in the air was especially disquieting 53 Unfortunately, the rea-sons for the deaths of Croce-Spinelli and Sivel were not clearly attributed to hypoxia Von Schrotter, an Austrian physiologist, believed Bert’s position regarding oxygen def-icit as the lethal threat and encouraged Berson to attempt further high-altitude balloon flights He originally devised

a system for supplying oxygen from a steel cylinder with tubing leading to the balloonists Later, von Schrotter con-ceived the idea of a face mask to supply oxygen more easily and also began to use liquid oxygen With these devices, Berson reached 36,000 ft in 1901 4 , 54

The Wright brothers’ historic flight at Kitty Hawk in

1903 substantially changed the nature of flight The tary value of airplanes soon was appreciated and applied during World War I The Germans were especially inter-ested in increasing the altitude limits for their pilots They applied the concepts advocated by von Schrotter and pro-vided liquid oxygen supplies for high-altitude bombing

FIGURE 1-12 A typical device used by Bert to study animals under low-pressure conditions (Used, with permission, from Bert 15 )

flights Interest in airplane flights for commercial and

mil-itary uses was especially high following Lindbergh’s solo

flight across the Atlantic in 1927 Much work was done

on valves and oxygen gas regulators in the hope of

fur-ther improving altitude tolerance A series of high-altitude

airplane flights using simple face masks and

supplemen-tal oxygen culminated in Donati’s reaching an altitude of

47,358 ft in 1934 This was clearly the limit for human

endurance using this technology 4 , 54

Somewhat before Donati’s record, a breakthrough in

flight was achieved by Piccard, who enclosed an aeronaut

in a spherical metal chamber sealed with an ambient

baro-metric pressure equivalent to that of sea level The

aero-naut easily exceeded Donati’s record and reached 55,000 ft

This work recapitulated the important physiologic

con-cept, gained from Bert’s earlier experimental work in

high-altitude chambers, that oxygen availability is a function of

both fractional inspired oxygen and barometric pressure

Piccard’s work stimulated two separate investigators to

adapt pressurized diving suits for high-altitude flying In

1933, Post devised a rubberized, hermetically sealed silk

suit In the same year, Ridge worked with Siebe, Gorman,

and Company to modify a self-contained diving dress for flight This suit provided oxygen under pressure and an air circulator with a soda lime canister for carbon diox-ide removal These suits proved quite successful, and soon pilots were exceeding heights of 50,000 ft Parallel work with sealed gondolas attached to huge balloons led to ascents higher than 70,000 ft In 1938, Lockheed produced the XC-35, which was the first successful airplane with

a pressurized cabin ( Fig 1-15 ) 4 , 54 These advances were applied quickly to military aviation in World War II The German Air Ministry was particularly interested in devel-oping oxygen regulators and valves and positive-pressure face masks for facilitating high-altitude flying 57

Work throughout World War II defined limits for nological support of high-altitude flight Pilots could reach

tech-up to 12,000 ft safely without oxygen stech-upplements Above this limit, oxygen-enriched air was essential With flights going above 25,000 ft, oxygen supplementation alone usu-ally was insufficient, and some type of pressurized sys-tem—cabin, suit, or mask—was needed Pressurization

as an adjunct, however, reached its limit of usefulness at approximately 80,000 ft At this altitude, air compressors

A

B E

D C a

a´

O

FIGURE 1-13 A bird placed in a low-pressure bell jar can supplement the enclosed atmospheric air with oxygen inspired from the bag labeled O Supplemental oxygen prolonged survival in these experiments (Used, with permission, from Bert 15 )

became too leaky and inefficient to maintain adequate

pres-surization A completely sealed cabin was essential to

pro-tect passengers adequately from the rarefied atmosphere

outside An altitude of 80,000 ft thus became a functional

definition of space because at this height complete control

FIGURE 1-14 The adventurous French balloonists Croce-Spinelli,

Sivel, and Tissandier begin their attempt at a record ascent The

balloonist at the right can be seen inhaling from an oxygen tank

Unfortunately, the supplemental oxygen did not prevent tragic results

from a too rapid ascent (Used, with permission, from Armstrong HG

Principles and Practice of Aviation Medicine Baltimore, MD: Williams

& Wilkins; 1939:4.)

FIGURE 1-15 Lockheed produced the XC-35 in 1938 This was

the first plane to have a pressurized cabin (Used, with permission,

Armstrong HG Principles and Practice of Aviation Medicine Baltimore,

MD: Williams & Wilkins; 1939:337.)

of the atmosphere in the plane (i.e., the supply of oxygen,

a means of removing carbon dioxide, and adequate control

of temperature and humidity) was required 58 , 59 Advances

in submarine ventilatory physiology were adapted to the space program In 1947, the American Air Force began the XI program, which culminated in the production in

1952 of the X15 aircraft This plane reached a top speed

of 4159 miles per hour at an altitude of 314,750 ft More importantly, the technology developed for this plane was

a prelude to manned satellite programs The United States Mercury and the Russian Vostok programs both relied

on rockets to boost small, one-person capsules into space orbit The Mercury capsule had a pure oxygen atmosphere

at a reduced cabin pressure In addition, the pilot wore

a pressurized suit with an independent, closed oxygen supply In April 1961, Gagarin was the first person to be launched into space Shepard followed soon after, in May

1961, and reached an altitude of 116 miles More ticated space flight—in the Gemini, Apollo, and space sta-tion programs—was based on similar ventilation systems and principles 60

MECHANICAL VENTILATION OF RESUSCITATION AND ANESTHESIA

Vivisection Galen described ventilating an animal as follows: “If you take a dead animal and blow air through its larynx [through

a reed], you will fill its bronchi and watch its lungs attain the greatest distention.” 61 Unfortunately, Galen failed to appreciate how ventilating the lungs could help him in his vivisection work Galen operated on many living animals, but his studies on the function of the heart were limited

by the risk of pneumothorax Opening the thoracic cavity almost certainly resulted in death of the animal 1 , 6 More than a thousand years later, Vesalius realized that ventila-tion could protect animals from pneumothorax 62 , 63 The lungs would collapse and the beating heart would almost stop when Vesalius opened the chest cavity, but the heart could be restarted by inflating the lungs through a reed tied into the trachea Paracelsus, a contemporary of Vesa-lius, is reported to have used a similar technique around

1530 in attempting to resuscitate a human Did Paracelsus adapt Vesalius’s research efforts, or vice versa? 63 It is also unclear whether Vesalius himself tried artificial ventila-tion during the dissection of a Spanish nobleman Legend has it that when the nobleman’s heart began to beat once more, Vesalius’s medical associates were so outraged that they reported him to the religious authorities Vesalius only avoided being burned at the stake by embarking on a pil-grimage to the Holy Land, but he died during the voyage 64 Presumably, Harvey became familiar with Vesalius’s use

of ventilation during vivisection because he mentioned artificial ventilation in his work later in England 63 Other English scientists soon after began to mention artificial